Re: Derivative help
- To: mathgroup at smc.vnet.net
- Subject: [mg39162] Re: Derivative help
- From: atelesforos at hotmail.com (Orestis Vantzos)
- Date: Fri, 31 Jan 2003 19:57:29 -0500 (EST)
- References: <b1dg35$7ar$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
To begin with, use proper Mathematica syntax to write the body of your function: Log[x]^x not ln(x)^x Even after that, Mathematica is rightfully confused since you don't specify the variable of the differentiation (that the expression should be differentiated as a function of x). There are two ways to work around this problem: The first is to define f as you do: f=Log[x]^x and then tell Mathematica to explicitly differentiate it as a function of x: D[f,x] The second way is to define f as a proper Mathematica function: Clear[f] (* to get rid of the previous definition *) f[x_]:=Log[x]^x Now you can write f'[x]. You can even go ahead and write f' but that will return a 'pure function' (look it up). Orestis "Steve Chiang" <stevezx at attbi.com> wrote in message news:<b1dg35$7ar$1 at smc.vnet.net>... > Hi, all. I'm new to Mathematica. I went to the help section for my > question but it only further confused me. I'm basically trying to take the > first derivative of (ln(x))^x. Here is my syntax: f = (ln(x))^x. But then > when I evaluate f ', it says nothing but ((ln(x))^x)' which is nothing new. > Is this because I didn't specify bounds and that the function may be > discontinuous over the default bounds in Mathematica? > > Thanks